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B and SarA independently regulate polysaccharide intercellular adhesin production in Staphylococcus epidermidis

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The production of polysaccharide intercellular adhesin (PIA) is an essential process in foreign body infections mediated by Staphylococcus epidermidis. Transcriptional regulation of the icaADBC operon, the genes responsible for production of enzymes that synthesize PIA, is multi-factorial and involves at least SarA and B. Transcriptional and promoter fusion studies revealed that the decreased transcription of the icaADBC operon observed in a S. epidermidis 1457 sigB mutant is not mediated through a direct interaction of B–RNA polymerase at the icaADBC promoter region but instead through the upregulation of IcaR, a known repressor of icaADBC transcription. Transcriptional analysis of a 1457 sigB–icaR double mutant confirmed that the decreased icaADBC transcript in 1457 sigB is IcaR dependent. Furthermore, primer extension studies suggest that the icaR promoter appears to be A dependent, suggesting that B indirectly controls icaR transcription through an unknown pathway. In addition, it was confirmed that the loss of SarA results in the loss of icaADBC transcription and PIA production in S. epidermidis. It was further demonstrated, through the over-production of SarA in 1457 sigB, that the loss of sarP1 promoter activity in 1457 sigB has little or no effect on the loss of PIA production in this mutant. Finally, it was demonstrated that PIA production could be restored in both 1457 sigB and 1457 sarA by complementing these mutants with a full-length icaADBC operon controlled by a cadmium-inducible noncognate promoter. It is concluded that B and SarA operate independently of each other to regulate PIA production and biofilm development in S. epidermidis.Key words: Staphylococcus epidermidis, biofilm, B, SarA, icaADBC.

La production de l'adressine intracellulaire PIA est un processus essentiel à l'infection transmise par Staphylo coccus epidermidis. La régulation transcriptionnelle de l'opéron icaADBC, le gène responsable de la production des enzymes qui synthétisent la PIA, est multifactorielle et implique au moins SarA et B. Des études de la transcription ainsi que des études de fusion du promoteur ont révélé que la diminution de la transcription de l'opéron icaADBC observée chez le mutant S. epidermidis 1457 sigB n'est pas causée par l'interaction directe B–ARN polymérase dans la région promotrice de icaADBC, mais est plutôt causée par l'activation de IcaR, un répresseur connu de la transcription de icaADBC. Une analyse transcriptionnelle du double mutant 1457 sigB–icaR a confirmé que la diminution du transcrit icaADBC chez le mutant 1457 sigB est dépendante de IcaR. Qui plus est, des études d'extension d'amorces suggèrent que le promoteur de icaR soit dépendent de A, suggérant que B contrôle indirectement la transcription de icaR par un mécanisme encore inconnu. De plus, nous avons confirmé que la perte de SarA résulte en la perte de la transcription de icaADBC et de la production de PIA chez S. epidermidis. Nous avons également démontré, à travers la surproduction de SarA chez le mutant 1457 sigB, que la perte de l'activité du promoteur sarP1 chez le mutant 1457 sigB n'a que peu ou pas d'effet sur la perte de production de PIA. Finalement, nous démontrons que la production de PIA ne peut être restaurée chez les mutants 1457 sigB et 1457 sarA par complémentation avec l'opéron icaADBC de pleine longueur placé sous le contrôle d'un promoteur hétérologue inductible par le cadmium. Nous concluons que B et SarA agissent indépendamment l'un de l'autre pour réguler la production de PIA et le développement de biofilm chez S. epidermidis.Mots clés : Staphylococcus epidermidis, biofilm, B, SarA, icaADBC.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2007-01-01

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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